The invention generally relates to optimizing charge phasing of a perforating gun.
For purposes of enhancing the production of well fluid from a subterranean formation, a device called a perforating gun typically is lowered down into the wellbore (that extends into the formation) to form perforation tunnels in the formation. The perforating gun includes radially-oriented shaped charges that are fired to form perforation jets that create these perforation tunnels. Typically, specified parameters called a shot density and a phasing angle control the number of shaped charges of the gun and the distances between the shaped charges. Most perforating gun phasing is spiral, which means that the shaped charges are located along a helical path that circumscribes the longitudinal axis of the perforating gun. In this spiral phasing pattern, adjacent shaped charges typically are spaced equally apart. Phasing patterns other than spiral phasing patterns are also conventionally used. For example, a conventional perforating gun may have a planar phasing pattern in which multiple shaped charges are arranged in planes, and these planes have surface normals that are parallel to the longitudinal axis of the gun.
As a more specific example, FIG. 1 depicts a cross-sectional view of a perforating gun 20 that has shaped charges that are arranged in a spiral phasing pattern. This spiral phasing pattern is shown in FIG. 2, a figure that depicts a schematic view of the perforating gun 20 along its longitudinal axis 21.
More particularly, FIG. 1 shows a top view of three exemplary shaped charges 10a, 10b and 10c of the perforation gun 20. Adjacent shaped charges, such as the shaped charges 10a and 10b (for example), are spaced 135° apart about the longitudinal axis 21 of the gun 20. Thus, the perforating gun 20 is said to have a 135° spiral phasing pattern. The distances between adjacent charges in this spiral phasing pattern establish the shot density (typically expressed as shots per foot (spf)) of the perforating gun 20. Therefore, for example, a greater shot density may be achieved by decreasing the distances between adjacent shaped charges. As depicted in FIGS. 1 and 2, the shaped charges of the perforating gun 20 extend along a helical path that completely circumscribes the longitudinal axis 21 of the gun 20.